Scramble parser should return Result

[stanleydesu]

https://github.com/V-Wong/CubeSimRS/blob/92ffac3c08fb3214013b29a1dd8cc495d4637855/src/scramble_parser.rs#L47
Should return Result instead of panicking, as the user can handle the error better.

[vwcwong]

Agree, will make change.